diff --git a/lib/Slic3r/GUI/SkeinPanel.pm b/lib/Slic3r/GUI/SkeinPanel.pm
index 6c4842ea..7644136b 100644
--- a/lib/Slic3r/GUI/SkeinPanel.pm
+++ b/lib/Slic3r/GUI/SkeinPanel.pm
@@ -247,7 +247,9 @@ sub load_config_file {
     $Slic3r::GUI::Settings->{recent}{config_directory} = dirname($file);
     Slic3r::GUI->save_settings;
     $last_config = $file;
-    $_->load_config_file($file) for values %{$self->{options_tabs}};
+    for my $tab (values %{$self->{options_tabs}}) {
+        $tab->load_config_file($file);
+    }
 }
 
 sub load_config {
@@ -265,7 +267,9 @@ sub config_wizard {
     return unless $self->check_unsaved_changes;
     if (my $config = Slic3r::GUI::ConfigWizard->new($self)->run) {
         if ($self->{mode} eq 'expert') {
-            $_->select_default_preset for values %{$self->{options_tabs}};
+            for my $tab (values %{$self->{options_tabs}}) {
+                $tab->select_default_preset;
+            }
         }
         $self->load_config($config);
     }
diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 8117f238..825e928f 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -266,7 +266,8 @@ sub make_perimeters {
                 $role = EXTR_ROLE_CONTOUR_INTERNAL_PERIMETER;
             }
             
-            if ($self->id > 0) {
+            ### Disable overhang detection for now
+            if (0 && $self->id > 0) {
                 # A perimeter is considered overhang if its centerline exceeds the lower layer slices
                 my $is_overhang = $is_contour
                     ? @{diff([$polygon], \@lower_slices)}
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index 917fa677..c6f404f1 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -188,10 +188,16 @@ sub validate {
         
         # check vertical clearance
         {
-            my @obj_copies = $self->object_copies;
-            pop @obj_copies;  # ignore the last copy: its height doesn't matter
-            my $scaled_clearance = scale $Slic3r::Config->extruder_clearance_height;
-            if (grep { +($_->size)[Z] > $scaled_clearance } map @{$self->objects->[$_->[0]]->meshes}, @obj_copies) {
+            my @object_height = ();
+            foreach my $object (@{$self->objects}) {
+                my $height = $object->size->[Z];
+                push @object_height, $height for @{$object->copies};
+            }
+            @object_height = sort { $a <=> $b } @object_height;
+            # ignore the tallest *copy* (this is why we repeat height for all of them):
+            # it will be printed as last one so its height doesn't matter
+            pop @object_height;
+            if (@object_height && max(@object_height) > scale $Slic3r::Config->extruder_clearance_height) {
                 die "Some objects are too tall and cannot be printed without extruder collisions.\n";
             }
         }
@@ -265,15 +271,6 @@ sub init_extruders {
     }
 }
 
-sub object_copies {
-    my $self = shift;
-    my @oc = ();
-    for my $obj_idx (0 .. $#{$self->objects}) {
-        push @oc, map [ $obj_idx, $_ ], @{$self->objects->[$obj_idx]->copies};
-    }
-    return @oc;
-}
-
 sub layer_count {
     my $self = shift;
     return max(map { scalar @{$_->layers} } @{$self->objects});